Method for detecting stressed state and stress detection apparatus

Abstract

A method for detecting a stressed state, including a step of detecting a stressed state of a subject based on a tomographic image of a choroid of the subject, and a stress detection apparatus including: an image acquisition unit that acquires a tomographic image of a choroid of a subject; a calculation unit that calculates a choroidal thickness or a volume of the choroid based on the tomographic image; and a detection unit that detects a stressed state of the subject based on the choroidal thickness or the volume of the choroid.

The invention claimed is: 
     
       1. A method for detecting a stressed state, comprising a step of detecting a stressed state of a subject based on a tomographic image of a choroid of the subject, wherein
 the tomographic image includes a region including a position below a fovea of a retina, or a region including a position away from the fovea by a predetermined distance in a predetermined direction with respect to the fovea of the retina, 
 the step of detecting a stressed state includes a step of detecting the stressed state of the subject based on a choroidal thickness at the position of the fovea of the retina, or the position away from the fovea by the predetermined distance in the predetermined direction with reference to the fovea of the retina, or based on a volume of the choroid calculated for a region centered around a position of the fovea of the retina, or the position away from the fovea by the predetermined distance in the predetermined direction with respect to the fovea of the retina, and 
 the stressed state is detected when the calculated choroidal thickness or the calculated volume of the choroid is higher than a reference value calculated in advance from tomographic images of the choroids of healthy bodies that are not in a stressed state. 
 
     
     
       2. The method for detecting a stressed state according to  claim 1 , wherein a stressed state is detected when the calculated choroidal thickness is no less than 300 μm at a position below a fovea. 
     
     
       3. The method for detecting a stressed state according to  claim 1 , wherein the step of detecting a stressed state includes a step of correcting the calculated choroidal thickness based on at least one factor selected from among a detection time, the subject's age, sex, and history of present illness, and an indicator obtained from an eye structure. 
     
     
       4. The method for detecting a stressed state according to  claim 3 , wherein the step of detecting a stressed state includes
 a step of calculating a correction coefficient related to the choroidal thickness in an unstressed group based on a ratio of a standard choroidal thickness to the calculated choroidal thickness, the standard choroidal thickness being calculated from a group of which the at least one factor has a standard value, or related to the volume of the choroid in an unstressed group based on a ratio of a standard volume to the calculated volume, the standard volume of the choroid being calculated from a group of which the at least one factor has a standard value; and 
 a step of correcting the choroidal thickness or the volume of the choroid using the correction coefficient to detect the stressed state of the subject. 
 
     
     
       5. The method for detecting a stressed state according to  claim 1 , wherein the step of detecting a stressed state includes a step of correcting the calculated volume of the choroid based on at least one factor selected from among a detection time, the subject's age, sex, and history of present illness, and an indicator obtained from an eye structure. 
     
     
       6. A stress detection apparatus (X) comprising:
 an image acquisition unit ( 11 ) configured to acquire a tomographic image of a choroid of a subject; 
 a calculation unit ( 13   b ) configured to calculate a choroidal thickness or a volume of the choroid based on the tomographic image; and 
 a detection unit ( 14 ) configured to detect a stressed state of the subject based on the choroidal thickness or the volume of the choroid, wherein 
 the tomographic image includes a region including a position below a fovea of a retina, or a region including a position away from the fovea by a predetermined distance in a predetermined direction with respect to the fovea of the retina, and 
 the detection unit ( 14 ) is configured to detect 
 the stressed state of the subject based on a choroidal thickness at the position of the fovea of the retina, or the position away from the fovea by the predetermined distance in the predetermined direction with reference to the fovea of the retina, or based on a volume of the choroid calculated for a region centered around a position of the fovea of the retina, or the position away from the fovea by the predetermined distance in the predetermined direction with respect to the fovea of the retina, and 
 the stressed state when the calculated choroidal thickness or the calculated volume of the choroid is higher than a reference value calculated in advance from tomographic images of the choroids of healthy bodies that are not in a stressed state. 
 
     
     
       7. The stress detection apparatus (X) according to  claim 6 , wherein the detection unit ( 14 ) is configured to
 calculate a correction coefficient related to the choroidal thickness in an unstressed group based on a ratio of a standard choroidal thickness to the calculated choroidal thickness, the standard choroidal thickness being calculated from a group of which at least one factor has a standard value, the at least one factor being selected from among a detection time, the subject's age, sex, and history of present illness, and an indicator obtained from an eye structure, or related to the volume of the choroid in an unstressed group based on a ratio of a standard volume to the calculated volume, the standard volume of the choroid being calculated from the group of which the at least one factor has a standard value; and 
 correct the choroidal thickness or the volume of the choroid using the correction coefficient to detect the stressed state of the subject.